A photo of Martin Luther King Jr., Robert Kennedy, and President Lyndon Johnson hangs on the wall as Julian Castro, mayor of San Antonio and democratic all-star, spoke with the press before visited with guests at the Commonwealth Club in San Francisco, Calif., on Monday, January 7, 2013. Along for the visit was his identical twin, Joaquin Castro.

Photo: Carlos Avila Gonzalez, The Chronicle

A photo of Martin Luther King Jr., Robert Kennedy, and President...

Image 4 of 7

Joaquin Castro applauds as his twin brother, Julian Castro, mayor of San Antonio and democratic all-star, speaks at the Commonwealth Club in San Francisco, Calif., on Monday, January 7, 2013. Along for the visit was his identical twin, Joaquin Castro.

Photo: Carlos Avila Gonzalez, The Chronicle

Joaquin Castro applauds as his twin brother, Julian Castro, mayor...

Image 5 of 7

Jesssica Weiss, left, Becca Caccavo, center, and Isabela Bowden, with Junior States of America, listen to Julian Castro, left, mayor of San Antonio and democratic all-star, as he visited with guests at the Commonwealth Club in San Francisco, Calif., on Monday, January 7, 2013. Along for the visit was his identical twin, Joaquin Castro.

Photo: Carlos Avila Gonzalez, The Chronicle

Jesssica Weiss, left, Becca Caccavo, center, and Isabela Bowden,...

Image 6 of 7

Julian Castro, mayor of San Antonio and democratic all-star, gestures as he speaks at the Commonwealth Club in San Francisco, Calif., on Monday, January 7, 2013. Along for the visit was his identical twin, Joaquin Castro.

Photo: Carlos Avila Gonzalez, The Chronicle

Julian Castro, mayor of San Antonio and democratic all-star,...

Image 7 of 7

Julian Castro, mayor of San Antonio and democratic all-star, waved to the crowd as he spoke at the Commonwealth Club in San Francisco, Calif., on Monday, January 7, 2013. Along for the visit was his identical twin, Joaquin Castro.

Democrats' hunger for fresh faces and Latino leadership in politics was on full display as San Antonio Mayor Julian Castro - last year's highly praised Democratic National Convention keynoter - found himself face to face with a crowd in San Francisco this week.

At a sold-out speech to the Commonwealth Club of California Monday, hundreds of people filled an overflow section to see the Latino leader and education reformer, who has been alternately described in recent media reports as the "Latino messiah," a potential partner on a Hillary Rodham Clinton-Castro "dream ticket" in 2016, and even "the next Obama."

With his identical-twin brother, Rep. Joaquin Castro of Texas - who accompanied him on a California trip that included a stop at their alma mater, Stanford University - the pair were mobbed by admirers.

The audience of 300 in San Francisco burst into enthusiastic applause at a mere mention of the suggestion that Julian Castro, 38, the first Latino to keynote a Democratic Party convention, consider a presidential race, as Barack Obama did in the aftermath of his star moment at the convention podium in 2004.

Castro was quick to tamp down expectations he could follow in Obama's footsteps, saying the notion is "very flattering."

"But I wouldn't put myself in the same league as President Obama," he said, shaking his head in an interview with The Chronicle. "Obviously, he's someone of unique talent and ability."

Asked if he ruled out a run for the White House, or even being part of a Democratic ticket in 2016, Castro said, without hesitation, that he had.

His brother, Joaquin, who is also the newly elected president of the House Democratic freshmen in the 113th Congress, had his own views.

"My brother would be great at anything he does," Joaquin Castro said. "I know that right now he's focused on doing the best for our city. One of the reasons we got into politics was that we wanted to do great things for our town. ... It's very special to us."

As Democrats and Republicans alike consider the impacts of the 2012 election - which underscored the rising clout of the Latino and youth vote - the brothers Castro are gaining a national profile as rising stars with dual potential to fire up the next generation of Democratic voters.

The frank talk, and their focus on education, drew raves at the San Francisco event.

Becca Caccavo, 16, a Junior Statesman from Balboa High, said she and a crowd of her friends suspended their preparations for a school prom last year to watch Castro's Democratic Convention address, in which he related how the brothers were the product of San Antonio's public schools, raised mostly by a single mother. Caccavo said the speech moved many of them to tears, and "I sent everyone links."

In his address, Julian Castro said their mother, a Latina activist, "dragged" the brothers to so many community events when they were children that "we hated politics."

Stanford experience

Their turnaround, he said, came in the Bay Area when the two - with the help of Pell Grants, work study and affirmative action - were admitted to Stanford University. Julian Castro said that with SAT scores of 1200, he couldn't compete with many students who applied to the university, and he credited affirmative action for opening the door.

At Stanford, he said, he saw "a community with a higher education level, higher income levels and focused on the technology" that would drive innovation, he recalled. "For the first time, I had the opportunity to compare San Antonio with another community."

The Republican Party, both men said, must understand Latinos who, like the Castros, value education as a stepping stone to the American dream - especially as many Republicans resist immigration reform and the Dream Act, which would allow children of undocumented immigrants to earn a path to citizenship.

"It's not just about electing a Ted Cruz, or a Marco Rubio, or a Susana Martinez," said Joaquin Castro, in a reference to some of the GOP's brightest stars. "It's not just about your sales people. It's the policies you're enacting."